Science Journal of Chemistry 2018; 6(4): 50-55

http://www.sciencepublishinggroup.com/j/sjc

doi: 10.11648/j.sjc.20180604.13

ISSN: 2330-0981 (Print); ISSN: 2330-099X (Online)

Syntheses, Geometrical and Electronic Structure of Alkyladamantanes and Their Thermodynamic Characteristic According to the Density Functional Theory

Amanzhan Saginayev1, *

, Marina Kursina2, Altynai Kalauova

2

1Laboratory of Petrochemistry, Atyrau of Oil and Gas University, Atyrau, Kazakhstan 2Department of Chemistry and Chemical Technology, Atyrau of Oil and Gas University, Atyrau, Kazakhstan

Email address:

*Corresponding author

To cite this article: Amanzhan Saginayev, Marina Kursina, Altynai Kalauova. Syntheses, Geometrical and Electronic Structure of Alkyladamantanes and Their

Thermodynamic Characteristic According to the Density Functional Theory. Science Journal of Chemistry. Vol. 6, No. 4, 2018, pp. 50-55.

doi: 10.11648/j.sjc.20180604.13

Received: September 3, 2018; Accepted: September 26, 2018; Published: October 22, 2018

Abstract: Propyladamantanes synthesized by of alkylation adamantane with isopropyl alcohol temperature range from 5 to

40°C in the presence of 96% sulfuric acid. Tetramethyl- and Dimethylethyladamantanes synthesized by of isomerization of

Perhydroanthracene in the presence of aluminium oxide catalyst on the setting of the flow type. Isomers Butyladamantanes

was obtained by the reaction of alkylation of the adamantane with n-butane and isobutane. Adamantane and its derivatives

have been the subject of many experimental and theoretical studies. The molecular structure of adamantane was studied by

gasphase electron diffraction, Penning ionization electron spectroscopy, photoelectron spectroscopy, electron spin resonance,

and quantum calculations of ionization potentials (IP) and electron affinity (SE). The structure 1-n-propyladamantane (1), 1-

isopropyladamantane (2), 2-n-propyladamantane (3), 1,2-di-n-propyladamantane (4), 1,3-dimethyl-5-ethyladamantane (5),

1,3,5,6-tetramethyladamantane (6), 1,3,5,7-tetramethyladamantane (7), perhydroanthracene (8), 1-n-butyladamantane (9), 1-

isobutyladamantane (10), 1-sec-butyladamantane (11) has been studied using the Becke–Lee–Yang–Parr (B3LYP) hybrid

energy functional of electron density with the 6-31G* basis set. The geometric and electronic characteristics of the compounds

and their total energy, normal vibration frequencies have been calculated. It has been shown that the calculated Gibb free

energies of formation for the perhydroanthracene isomerization products are in qualitative agreement with the experimental

product composition of the isomerate and alkylation of adamantane with isopropyl alcohol are in qualitative agreement with

the experimental composition of the products. Obtained good agreement of calculated and experimental data on the

composition of equilibrium mixtures.

Keywords: Propyladamantane, Dimethylethyladamantane, Tetramethyladamantane, Butyladamantane,

DFT Calculations

1. Introduction

Alkyladamantanes and higher alkyldiamondoids, are of

interest not only as a component of energetic hydrocarbon

fuels, e.g., RF-1, RF-2, etc. propellants, but also have great

scientific importance. Because of the special thermodynamic

properties of their isomers, they can be used for assessing the

degree of catalytic transformation of oils and condensates by

the action of natural clays and aluminosilicates and

“fingerprinting” the fuels manufactured on their basis. In

addition, these hydrocarbons are useful as feedstock in fine

organic and petrochemical syntheses [1]. The molecular

structure of adamantane was studied by gasphase electron

diffraction [2], Penning ionization electron spectroscopy [3],

photoelectron spectroscopy [4], electron spin resonance [5],

and quantum calcu lations of ionization potentials (IP) and

electron affin ity (SE) [6]. Since obtaining experimental data

on the relative thermodynamic stability of isomers of

polyalkyladamantanes and higher alkyldiamondoids is

fraught with certain difficulties, including those in the

51 Amanzhan Saginayev et al.: Syntheses Geometrical and Electronic Structure of Alkyladamantanes and Their

Thermodynamic Characteristic According to the Density Functional Theory

identification of the isomers and determination of their

spatial structure, computational methods are anticipated to

play a very important role in solving these problems. In a

previous papers [7, 8], we reported the results of studying the

structure of perhydroacenaphthene, perhydrofluorene and its

isomerization products С12Н20-С13Н22 alkyladamantanes

and presented calculated geometric and electronic

characteristics, total energies, transformation energies,

entropies of transformations, and normal vibration

frequencies, as well as the equilibrium constant of

isomerization of perhydroacenaphthene and perhydrofluorene

into products.

In this paper we discuss the results of our quantum-

chemical study of propyl-, tetramethyl-, dimethylethyl- and

butyladamantanes, including comparison of the calculated

and experimental compositions of equilibrium mixtures.

2. Experimental

2.1. The Synthesis of Alkyladamantanes

Propyladamantanes were synthesized by alkylation of

adamantane with isopropyl alcohol according [9] to figure 1.

The reaction was carried out in the temperature range from 5

to 40 ° C in the presence of 96% sulfuric acid.

Figure 1. Synthesis of propyl- and dipropyladamantanes.

The main products of the alkylation of adamantane with

isopropyl alcohol are 1-n-propyladamantane (yield 24%, n�

��

= 1.4902) and 1,3-dipropyladamantane (yield 18%, n�

�� =

1.4882), and in small amounts 1-isopropyl- and 2-n-

propyladamantanes (yield 10% and 1%, respectively).

The structure of propyl radicals is clearly determined by

IR spectra of hydrocarbons. The presence of the n-propyl

group is indicated by the ordinary character of the 1380 cm-1

band and the 740 cm-1

band (Figure 2). The asymmetry of the

1380 and 1530 cm-1

bands is associated with an impurity of

1-isopropyl adamantane.

Based on the composition of the alkylation products of

adamantane with alcohols, the following reaction mechanism

can be assumed. Alkylation proceeds along the tertiary

carbon atom of the adamantane nucleus. The formation of a

carbonium ion and the transfer of a positive charge to

adamantane with the formation of an adamantyl-cation can

be represented by the following scheme:

CH� � CHOH � CH� �

�

�� CH� � C�

H � CH� � H�O

In addition, the alcohol is dehydrogenated to the

corresponding olefin and attached along the nucleophilic

mechanism to the adamantyl cation:

CH� � CHOH � CH� �����

���� CH� � CH � CH� � H�O

Figure 2. The experimental IR spectra of 1-n-propyladamantane.

Tetramethyl- and dimethylethyladamantanes of the

composition C14H24 (5-7) were isomerized from

perhydroanthracene [10], according to figure 3. The

isomerization of perhydroanthracene was carried out at a

temperature of 180-200°C in the presence of aluminum

oxide.

Figure 3. Synthesis of dimethylethyl- and tetramethyladamantanes by

isomerization of perhydroanthracene.

The main reaction products are 1,3,5,6-

tetramethyladamantane (yield 25%, n�

�� = 1.4800) and 1,3-

dimethyl-5-ethyladamantane (yield 35%, n�

�� = 1.4805). The

formation of the thermodynamically most stable isomer -

Science Journal of Chemistry 2018; 6(4): 50-55 52

1,3,5,7-tetramethyladamantane kinetically is extremely

difficult (yield 9%).

The structure of methyl and ethyl radicals is also clearly

defined by IR spectroscopy [12, 13].

The mechanism of isomerization of perhydroanthracene

can be schematically represented by the following scheme:

Alkylation of adamantane with isooctane was carried out

in a swinging duck, thermostated at a given temperature. The

adamantane was dissolved in isooctane and AlCl3 was added.

The catalyst was activated with hydrochloric acid. The

reaction was carried out for 2 hours. The main products are

1-n-butyladamantane (yield 66%, n�

�� = 1.4907), 1-

isobutyladamantane (yield 18%, n�

�� = 1.4890), 1-sec-

butyladamantane (yield 9%, n�

�� = 1.4870). The reason for

the lower thermodynamic stability of 1-isobutyl- and 1-sec-

butyladamantane is probably the spatial 1.5-interaction of the

protons of the methyl groups of the side chain and protons in

the second carbon of the adamantane nucleus.

On the basis of the experimental data, the difference in the

enthalpy of 1-n-butyl- and 1-isobutyl adamantanes is ≈ 10.3

kJ/mol.

Isomeric butyladamantanes (9-11) were obtained by the

alkylation reaction of adamantane with isooctane [11]. The

reaction equations are given in figure 4.

Figure 4. Synthesis of butyladamantanes.

Identification of reaction products was carried out using

mass-spectrometry, IR- and PMR-spectroscopy [12, 13].

Based on the studies carried out, it is possible to present

the following mechanism for the formation of

alkyladamantanes. The decomposition of paraffinic

hydrocarbons in the presence of AlCl3 occurs along the

heterolytic pathway. In this case, the C = C bonds, which are

closer to the center of the molecule, are most easily exposed

to the discontinuity.

Adamantane in the presence of AlCl3 readily forms

adamantyl cation, which reacts with the products of the

decomposition of paraffins (anion or olefin):

Alkyladamantanes under the reaction conditions are

isomerized with a change in structure:

2.2. Quantum-chemical Calculations of the Synthesized

Alkyladamantanes

Quantum-chemical calculations of compounds I-XI were

performed using the density functional theory (DFT) using

the B3LYP hybrid functional from the electron density with

total energy optimization and calculation of the frequencies

of normal vibrations and the 6-31G * basis set. Calculations

were performed using the program GAUSSIAN-98 [14]. For

each molecule, geometric parameters of atoms were

optimized using analytical methods of calculation.

Calculating the frequencies of normal vibrations using the

second derivatives, it was confirmed that the stationarity

points, determined in optimization of geometry, corresponded

to the minima of the potential energy surface.

The DFT B3LYP method is a combination of the Hartree–

Fock method and the density functional theory using Becke’s

three-parameter (B3) gradient-corrected functional series

[15] and the Lee–Yang exchange-correlation functional series

(LYP) [16]. For each molecule, the geometric arrangement of

atoms was optimized using analytical calculation methods.

By calculating the normal vibration frequencies with the use

of second derivatives, it was confirmed that the stationary

points determined with geometry optimization are energy

minima.

The DFT method using the B3LYP hybrid functional is

widely used in the study of the kinetics and mechanism of

reactions [17], the calculation and interpretation of

vibrational spectra, the thermodynamics of compounds [18,

19], the molecular structure [20-22], the structural and

electronic characteristics of compounds [23] and in other

cases of research.

3. The Results of Calculations and Their

Discussion

Table 1 shows the calculated electronic characteristics of

the calculated molecules (1-11). Here are the energies of the

boundary orbitals (Ehomo, Elumo), dipole moments (µ), zero-

point energy (ZPC) and entropy values (S).

53 Amanzhan Saginayev et al.: Syntheses Geometrical and Electronic Structure of Alkyladamantanes and Their

Thermodynamic Characteristic According to the Density Functional Theory

Table 2 shows the basic calculated energy characteristics

of compounds 1-11. Here are values of complete energies

(Et), complete energies with allowance for zero-point energy

(Ezpc), complete energies with allowance for enthalpy

corrections (EH) and complete energies with allowance for

Gibbs free energy corrections (EG) in atomic units.

Table 1. Basic design the electronic characteristics of compounds 1-11.

Compound Ehomo, ev Elumo, ev µ, D ZPC, ev S, cal/mol⋅K

1 -0.24781 0.10188 0.1275 0.334733 108.667

2 -0.25001 0.08986 0.1236 0.331388 107.244

3 -0.24958 0.08836 0.1444 0.330616 107.239

4 -0.24906 0.06401 0.0772 0.306013 100.098

5 -0.25075 0.06379 0.1090 0.305508 100.056

6 -0.25047 0.06518 0.1450 0.306382 101.521

7 -0.24864 0.06577 0.0219 0.306100 99.872

8 -0.25324 0.08626 0.0098 0.330032 106.630

9 -0.25559 0.07514 0.0808 0.307316 103.962

10 -0.25327 0.06330 0.1036 0.304719 100.113

11 -0.25170 0.06446 0.0945 0.306018 100.965

These thermodynamic quantities are defined by the

following formulas [24]:

Ezpc = Et + ZPC (1)

EH = Et + ZPC + Evib + E rot + E trans (2)

EG = EH - T S (3)

where, Evib – energy of oscillatory motion,

Erot – energy of rotational motion,

Etrans – energy of translational motion,

S – entropy,

T – temperature on the Kelvin scale.

Table 2. Basic calculation of energy characteristics of compounds 1-11 in atomic units at the temperature of 298.15 oK.

Compound Et, a.u., (∆Et) Ezpc, a.u., (∆Ezpc) EH, a.u., (∆EH) EG, a.u., (∆EG)

1 -547.8747539 -547.515212 547.501936 -547.553567

2 -547.8886614 -547.532903 -547.519003 -547.569958

3 -547.8883602 -547.533431 -547.519311 -547.570263

4 -547.8929792 -547.538677 -547.524623 -547.575287

5 -508,6655207 -508,336111 -508,323859 -508,372736

6 -508,6629781 -508,333033 -508,320840 -508,369816

7 -508,6612079 -508,331759 -508,319590 -508,367885

8 -508,6605242 -508,330749 -508,318633 -508,367042

9 -547.882752 -547.524897 -547.511158 -547.564131

10 -547.8794548 -547.521779 -547.508283 -547.559734

11 -547.8773523 -547.519630 -547.505964 -547.557543

Isopropyladamantane

1,3,5,7- Tetramethyladamantane

Science Journal of Chemistry 2018; 6(4): 50-55 54

Perhydroanthracene

1- Isobutyladamantane

Figure 5. The geometric structure of 1-isopropyladamantane,

perhydroanthracene, 1,3,5,7-tetramethyladamantane and 1-

isobutyladamantane.

The thermodynamic characteristics obtained from our

calculations are in qualitative agreement with the experimental

data [25] of the isomerization of perhydroanthracene.

Compound (7) as the product of isomerization has the greatest

thermodynamic stability from all the others (5, 6), since it has

the lowest values of Et, Ezpc, EH, EG, which also agrees with the

experiment. The calculated data show that the yields of various

alkyl adamantanes having the general formula C14H24 in the

isomerization reaction of perhydroanthracene are due to the

difference in their thermodynamic stability. Proceeding from

this, it can be concluded that this reaction is equilibrium. The

experimental yields of these products are consistent with our

calculations.

Figure 5 shows obtained from calculations the geometric

structures of molecules 2, 7, 8 and 10. Here, for each

structure, the nearest interatomic distances in angstroms are

indicated.

4. Conclusions

The geometrical structure, electronic and energy

characteristics (energy of boundary orbitals, dipole moments,

zero-point energy, entropy values, values of total energies) of

compounds (1-11) are calculated by the method of the

density functional theory (DFT) using the B3LYP hybrid

functional in 6-31G * bases.

It was found that the calculated values of the Gibbs

energies of the products of the isomerization of

perhydroanthracene and the alkylation of adamantane with

alcohols are in qualitative agreement with the experimental

composition of the products in isomeratees.

The applicability of the calculation methods used for

hydrocarbons of a diamond-like structure is shown and,

consequently, these methods can later be used to determine the

structure, thermodynamic stability, and compositions of

equilibrium mixtures of isomers of higher alkyldiamondoids, both

contained in oils and gas condensates, and obtained synthetically.

Acknowledgements

We Express our gratitude to Professor Yu. A. Borisov for

his help in calculations of thermodynamic characteristics of

alkyladamantanes.

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